Static pressure measurements in A 30 kWe class arcjet
01 Jun 1991-
TL;DR: In this article, a series of cold and hot flow static pressure measurements have been made as a function of distance along the principal axis of a 30 kWe arcjet, and it was shown that anode arc attachment points directly coincided with the minimum static pressure points.
Abstract: A series of cold and hot flow static pressure measurements have been made as a function of distance along the principal axis of a 30 kWe arcjet. During these experiments, the background pressure was varied from atmospheric pressure to less than 1 Torr. The experimental arcjet used in these tests had the same constrictor and conical nozzle dimensions as the baseline MOD-1 ammonia arcjet developed at NASA-JPL, but used nitrogen as the propellant gas. Comparison of the measured static pressure profiles with the arc erosion patterns on the anode surface showed that anode arc attachment points directly coincided with the minimum static pressure points. The dual voltage modes commonly observed in 30 kWe class arcjet thrusters are also believed to be caused by the presence of two pressure minima in the arcjet, one at the constrictor entrance and the other in the expansion nozzle. The static pressure profiles also suggest that the sonic flow transition occurs at the entrance to the nozzle, indicating the existence of very thick boundary layers in the arcjet constrictor.
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TL;DR: An overview of the basic principles of arcjets and arc heaters for readers unfamiliar with the field can be found in this paper, with an emphasis on common research areas and a guide to the organization of scientific research serving both arcjet and arc-heater development.
Abstract: Arcjets and arc heaters are important to a number of government-sponsored aerospace programs and share several common features. Placing satellites in orbit, maintaining proper orbit, and repositioning are major spacecraft mass drivers for a wide range of missions. Arcjets can reduce mission propulsion requirements in many cases and are of interest to many satellite users. Arc heaters are critical to the future development of hypersonic combat aircraft. Design and construction of a hypersonic aircraft for speeds of 4-5 km/s (Mach 12-15) will be complex and will require the development of high-performance arc-heating facilities for the evaluation/validation of new airframe and propulsion technologies. The first objective of this overview is to provide a summary of the basic principles of arcjets and arc heaters for readers unfamiliar with the field. The second objective is to describe fundamental research required to overcome the limitations of both devices, with an emphasis on common research areas. This overview is not comprehensive, but does include national research and development activities. It is intended as a guide to the organization of scientific research serving both arcjet and arc-heater development communities.
54 citations
TL;DR: In this paper, a review of past experimental measurements of internal flow properties of arcjet thrusters is presented, including measurements of cathode temperature, as well as static pressure, flow temperatures (vibrational, rotational, electronic, translational), electron density, and velocity throughout the interior region.
Abstract: We review past experimental measurements of internal flow properties of arcjet thrusters. These measurements are generally classified as either intrusive, requiring design changes to prototype thrusters, or nonintrusive, and include measurements of cathode temperature, as well as static pressure, flow temperatures (vibrational, rotational, electronic, translational), electron density, and velocity throughout the interior region extending to the exit plane. Comparisons are made to available model predictions. These measurements, performed on a wide range of thrusters, and operating on variety of propellants, indicate that the nozzle plasma flow may be removed from local thermodynamic equilibrium.
20 citations
27 Jun 1994
TL;DR: In this article, a numerical and experimental investigation of axial emission of a 5 kW class radiatively-cooled hydrogen arcjet thruster is presented, taking into account graybody thermal emission from the cathode and plasma radiation from hydrogen atoms and free electrons.
Abstract: A numerical and experimental investigation of the axial emission of a 5 kW class radiatively-cooled hydrogen arcjet thruster is presented. The complete visible spectrum is modeled, taking into account graybody thermal emission from the cathode and plasma radiation from hydrogen atoms and free electrons. The cathode temperature and the arc electron number density are obtained from the measured emission spectrum. The cathode temperature is found to be in the neighbourhood of the melting point of tungsten and increases with arcjet power at a constant massflow rate, suggesting an increase in the current density at the arc attachment point. The measured near-cathode electron number density is also found to increase with power, suppofling the idea of an increasing arc current density with arcjet power. The measured and modeled arc electron densities are, however, in discrepancy by a factor of approximately three.
9 citations
20 Jun 1994
TL;DR: In this paper, a review of past experimental measurements of internal flow properties of arcjet thrusters is presented, including measurements of cathode temperature, as well as static pressure, flow temperatures (vibrational, rotational, electronic, translational), electron density, and velocity throughout the interior region.
Abstract: We review past experimental measurements of internal flow properties of arcjet thrusters. These measurements are generally classified as either intrusive, requiring design changes to prototype thrusters, or nonintrusive, and include measurements of cathode temperature, as well as static pressure, flow temperatures (vibrational, rotational, electronic, translational), electron density, and velocity throughout the interior region extending to the exit plane. Comparisons are made to available model predictions. These measurements, performed on a wide range of thrusters, and operating on variety of propellants, indicate that the nozzle plasma flow may be removed from local thermodynamic equilibrium.
9 citations
01 Jul 1992
TL;DR: In this article, a series of experiments aimed at studying the temporal behavior of dc arcs on a water-cooled radially-segmented 30 kW class arcjet anode was performed.
Abstract: The long-term operational lifetime of most medium to high power arcjets is currently limited by the rapid deterioration of the arcjet electrodes. To a large extent, the rate of this deterioration is related to the motion of the arc discharge on the electrode surfaces. This paper details a series of experiments aimed at studying the temporal behavior of dc arcs on a water-cooled radially-segmented 30 kW class arcjet anode. The experimental anode used for these tests was made of copper, and was divided into four equivalent radial segments which were electrically isolated with aluminum oxide gaskets. The current carried by each segment was measured independently using four calibrated resistive shunts, and was analyzed by digital computer. The tests were limited to nitrogen propellant over a current range of 100-250 A dc. Results show that for the range of total currents considered here, the current distribution in the segmented arcjet anode is generally asymmetric, exhibiting random fluctuations over a wide range of frequencies.
3 citations
References
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TL;DR: In the case of collision-dominated, high-pressure arcs, the important role of radiative energy transfer, including strong self-absorption, has been established through the experimental and theoretical study of cylindrically symmetric, uncontaminated arc plasmas as mentioned in this paper.
Abstract: Progress in the physics of high-power arcs has been largely due to a blend of detailed experimental and theoretical investigations aimed at explaining the electrical behaviour of the discharge in terms of fundamental physical processes. In the case of collision-dominated, high-pressure arcs the important role of radiative energy transfer, including strong self-absorption, has been established through the experimental and theoretical study of cylindrically symmetric, uncontaminated arc plasmas. As a result, an insight has been gained into the additional complications produced in naturally occurring high-pressure arcs by electrode vapour contamination and self-magnetically-propelled plasma flows. The application of similarity theory based upon the conservation equations of fluid mechanics has produced good correlation of the properties of arcs in transverse flows and magnetic fields under a number of different operating conditions. Criteria defining stable arc operation have been derived using stability theory whilst axisymmetric instabilities of arcs in accelerating flows have been related to vortex production at the arc boundary.
85 citations
TL;DR: In this paper, a DC electric arc in superimposed gas flow behavior in arc tunnel, discussing electrode geometry is discussed. But the authors do not discuss the geometry of the arc tunnel.
Abstract: DC electric arc in superimposed gas flow behavior in arc tunnel, discussing electrode geometry
64 citations
TL;DR: In this paper, the boundary layer integral method at its second level of approximation has been used to study the DC arc in a supersonic nozzle flow and it is shown that with the inclusion of the arc momentum balance, the critical point of the flow is, generally, not the sonic points of the external flow.
Abstract: The boundary layer integral method at its second level of approximation has been used to study the DC arc in a supersonic nozzle flow. It is shown that with the inclusion of the arc momentum balance, the critical point of the flow is, generally, not the sonic point of the external flow. The speed, at which a disturbance propagates relative to the external flow, is in general supersonic and is dependent on the arc conditions. The arc model is capable of predicting the axial electric field, the arc size and the axial pressure distribution as a function of current. For affinely related nozzles, the solution is determined by a parameter N, which is related to zt, the stagnation condition and the nominal current density at the throat (I/At). Numerical results are given for a particular nozzle shape although the method of analysis is general. Practical implications as regards nozzle design for a gas blast circuit breaker are briefly discussed.
13 citations
18 Jul 1990
9 citations
01 Nov 1987
TL;DR: In this paper, the authors evaluated the lifetime and performance of a 30-kWe constricted arc ammonia arcjet for a 50-hour test with the goal of evaluating the performance of the arcjet.
Abstract: : The objective of this effort was to evaluate the lifetime and performance of a 30-kWe constricted arc ammonia arcjet This engine was based on a design developed by Avco Corporation in 1963 that delivered 978 seconds of specific impulse with ammonia during a 50-hour test After 573 hours of operation, a short circuit between the cathode and anode of JPL's thruster forced the life test to end Throughout the 573-hour test, the thruster operated at 249 kWe, delivering 229 N (015 lbs) of thrust, 865 seconds of specific impulse, and 37% efficiency Although the lifetime of JPL's thruster fell short of AFAL's original 1500-hour goal for the effort, the arcjet demonstrated a duration of over eleven times the lifetime of the 1963 Avco arcjet Further, the demonstrated lifetime of 576 hours is adequate for many orbit raising missions Keywords: Electric propulsion; Electrothermal arcjet, Space propulsion
8 citations